Extracorporeal lithotripters for the disintegration of kidney stones and the like without bodily invasion are well known in the art. Such lithotripters typically comprise a truncated ellipsoidal reflector. Either the entire apparatus is under water, as is a pertinent part of the patient, or a rubber diaphragm seals the otherwise open end of the lithotripter reflector. The reflector is filled with water. A pair of electrodes are spaced apart precisely at the first focal point of the reflector with the second focal point exterior the reflector beyond the diaphragm and designed to be placed on the kidney stone or other bodily concretion that is to be disintegrated. A high voltage spark across the gap between the electrode tips generates a shock wave which is focused by the walls of the reflector on the remote or second focus point. The shock wave energy so focused on the kidney stone or the like in due course reduces it to small fragments which readily pass from the body with the urine.
In many lithotripters external stone-locating devices are used, such as X-rays, or ultrasound. The detecting apparatus is often connected through a computer to positioning apparatus for the lithotripter reflector, and the reflector is mechanically brought in to proper position to place the second focus point on the kidney stone or other bodily concretion. The use of computers and mechanical controls renders the total cost of the lithotripter quite high, and beyond the purchasing power of some hospitals and clinics that would like to have one.
It is known that the reflector can be aimed by means of an ultrasound device in which an ultrasound transducer is disposed within the reflector for aiming of the reflector without the usual mechanical connections and computer, see for example U.S. Pat. No. 4,620,545 by Shene, Nowacki and Brisson. The ultrasound transducer presents a problem of mounting, in that it must be precisely aimed in the same direction as the focus of the reflector, and in that it is necessarily exposed to the shockwaves, and therefore subject to damage thereby.